Fears about a "chemical spill" led to the evacuation of a train at Honor Oak Park travelling from Croydon into central London, according to a passenger.

There are cancellations and delays to trains between East Croydon and London Bridge on Sunday (November 25) because British Transport Police are responding to an incident.

This is also affecting London Overground trains from West Croydon towards New Cross.

There was earlier confusion about the number of incidents happening on the rail network, after earlier reports of a trespass on the tracks affecting the London Overground between West Croydon and New Cross.

Now though a Croydon passenger has revealed he was on a Thameslink service which was halted and evacuated by police.

Emergency services on the tracks near Honour Oak Park after a train between Croydon and London Bridge was evacuated on Sunday, November 25 (Image: @GreenPeterU)

Peter Underwood was trying to get to a Green Party meeting in Elephant and Castle when the train he was on had to be evacuated.

He said: "We were evacuated near Honour Oak Park, so we had to get off and walk the 100 yards or so back to the platform.

"From what I can make out from other passengers some guy was reportedly being aggressive and shouting.

"He then [allegedly] dropped some sort of chemical on the floor and let himself out through the doors."

Peter had earlier tweeted: "Stuck on a train into London Bridge because someone spilt some 'liquid' over the floor and then left the train. Everyone safe, just waiting for emergency services to arrive and check things out."

Peter understood why the police had to investigate such an incident.

He added: "It was sensible for it to be investigated but it seems as though whatever he dropped turned out to be completely harmless.

"Apparently the person just jumped off but I wasn't in that carriage."

Passengers queueing to evacuate a Thameslink train travelling between Croydon and London Bridge on November 25, 2018 (Image: @GreenPeterU)

The National Rail website refers only to a "disturbance" on a Thameslink train causing much of the disruption on the trains on Sunday (November 24).

Information on National Rail just before 11am states: "A passenger was causing a disturbance on a Thameslink service travelling towards Peterborough earlier today.

"To allow emergency services to attend the train had to terminate early while it was between East Croydon and London Bridge.

"The electrical power supply is currently switched off and the lines are blocked to trains while the British Transport Police deal with the incident."

There are also reports of a disturbance between Sydenham and New Cross Gate.

The British Transport Police has been contacted for comment, and for further information on the number of incidents causing delays.

Where possible, services towards London Bridge will be diverted to London Victoria or run via alternative routes. Some trains will be terminated short of their destination, according to National Rail.

Thameslink services into London from Bedford or Peterborough will be terminating early until the disruption clears.

Southern services between London Bridge and Crystal Palace will be suspended until further notice.